private static void Add(string path, TreeNode node)
        {
            var childNode = new TreeNode {Text = path};
            node.Nodes.Add(childNode);
            try
            {
                foreach (var item in Directory.GetDirectories(path))
                {
                    Add(item, childNode);
                }
            }
            catch
            { }
        }

        private void tvCatalog_BeforeExpand(object sender, TreeViewCancelEventArgs e)
        {
            try
            {
                foreach (var file in Directory.GetFiles(e.Node.Text))
                {
                    e.Node.Nodes.Add(file);
                }
                if (e.Node.NextNode == null) return;
                {
                    foreach (TreeNode node in e.Node.Nodes)
                    {
                        if (!Directory.Exists(node.Text)) continue;
                        foreach (var file in Directory.GetFiles(node.Text))
                        {
                            node.Nodes.Add(file);
                        }
                    }
                }
            }
            catch
            { }
        }

        private void setdirs_Click(object sender, EventArgs e)
        {
            var disks = DriveInfo.GetDrives();
            var parentNode = new TreeNode();
            parentNode = tvCatalog.Nodes[0];
            foreach (var info in disks)
            {
                Add(info.ToString(), parentNode);
            }
        }